1. Field of the Invention
The present invention relates generally to magnetic head carriage and support apparatus for floppy disk drives and the like, and more particularly, to an improved carriage and head suspension mechanism wherein the spring forces exerted upon a pair of read/write heads is limited to the forces applied by small light-weight load springs, and the inertial forces are limited to those introduced by the mass of the heads and suspensions alone.
2. Description of the Prior Art
Conventional magnetic read/write head carriage devices have in the prior art been embodied in numerous forms including those types which are intended to carry a single head for reading one side of a floppy disk and those designed to carry dual heads intended to allow both sides of the disks to be read and written to. The most popular type in the latter category has been those which are of the type disclosed in the U.S. Pat. No. 4,151,573, S. L. Tandon et al., in which the lower head is rigidly attached to the carriage and caused to penetrate the plane of the recording media. The other head is gimbal-mounted to a flexure attached to a spring loaded arm that, when rotated into its operable position, serves to apply a predetermined force to the upper head sufficient to obtain media compliance.
Problems associated with such devices are: (1) the lower head must be positioned to at all times penetrate the plane of the media at close tolerance, thereby requiring inordinately tight manufacturing process controls; (2) variations of head load force due to the weight of the upper head support arm with respect to the drive mounting position; and (3) the effects of head inertia on the media. The effect of item (1) above is that it causes an unacceptable ratio of design parameter sensitivity to manufacturing process control. Items (2) and (3) tend to reduce potential media life.
One attempt to avoid the need for having one head pierce the nominal mid-plane of the media is disclosed in the U.S. Pat. No. 4,209,813, to P. S. Bryer, wherein two gimbal-mounted heads are biased into engagement with opposite sides of the media. However, in this device the heads are supported by flexures that are biased to normally move the heads away from each other, and spring biased load arms are used to load the heads onto the media.
A problem common to both of the above described prior art devices is that since the head load is applied by the spring (or springs) that bias the head carrying arm, or arms, into their media engaging position, movement of the head will bring into play not only the forces due to the inertia of the head, but also those associated with the mass of the load arm, or arms. These forces likewise can have a substantial influence on the life of the media.